The development of operating frequency for wireless communication, such as radio, TV broadcasting system, and cellular phone, has oriented toward the broadband applications, such as digital video broadcasting, ultra wide band, and etc. The design for broadband antenna is required to improve the shape and minimize the size, especially for antenna for consumer electrical products.
Conventional dipole antenna is a basic configuration for antenna structure. In theory, the positive and negative charges are oscillated between the dipole, thereby generating the electromagnetic (EM) radiation. The oscillation mechanism is limited by the physical dimension such as length. Typically, the length between the dipole is the integral multiple half-wavelength of EM wave. The available operating frequency is extremely narrow; hence it is unlikely to be introduced in broadband communication.
The Bowtie dipole antenna is one of the conventional antennas that are capable of being operated for wide-band application. In the scheme, the antenna becomes wider gradually from the feeding point to both sides to form a bowtie shape, wherein the feeding point is the center of the bowtie. Since this antenna has divergent current distribution, the operating bandwidth is extended. However, the current distribution is mainly caused by edge condition, therefore, there are innate limitations to the bandwidth, radiation pattern, and feeding impedance match.